1. Field of the Invention
This invention relates to a method for the synchronous operation of a plurality of juxtaposed cylinder devices. More particularly, it is concerned with such cylinder devices for operating a lift.
2. Description of the Prior Art
According to a known method intended for the synchronous operation of a plurality of juxtaposed cylinder devices which are operated by fluid pressure, their movable parts are mechanically connected to one another so as to move together synchronously and thereby achieve the synchronous operation of the devices. This method has, however, the drawback of complicating in construction the cylinder devices and the apparatus in which they are employed, and requiring an additional space for the installation of the necessary mechanism.
In the event that there is any spatial or other limitation that disables such mechanical synchronization, there is also known a method which employs a distributing valve to distribute an operating fluid uniformly to all cylinder devices. This valve is usually positioned close to a source of fluid supply and is, therefore, much less likely to complicate the cylinder devices or the apparatus in which they are employed. It does not form any obstacle to the operation of those devices or apparatus, or the external appearance thereof. The conventional method employing such a valve, however, has a serious drawback. If the reciprocating movement of the piston rods is repeated when they stay in their intermediate positions relative to their stroke, some positional difference or other unavoidably arises from one piston rod to another. This difference usually amounts to a range of 2 to 5 percent of the length of their stroke. It is necessary to move all of the piston rods to either end of their stroke to eliminate any such difference and thereby restore their synchronous operation.
A high accuracy of synchronism can be expected if an electrohydraulic servo mechanism is employed to control the supply of an operating fluid to cylinder devices. This method cannot however, be expected to be widely adopted, since the servo mechanism is expensive and its proper and effective application requires a high level of technology.